Manufacture of catalysts



Patented July 1-4, 1942 MANUFACTURE OF CATALYSTS Edward C. Lee and Jacob Elston Ahlberg, Chicago,

No Drawing.

This invention relates particularly to the manufactureof catalysts suitablefor accelerating reactions among hydrocarbons.

More specifically it has reference to a method for manufacturing refractory catalytic materials which are particularly efiective in selectively promoting theformation of gasoline boiling range liquids from relatively heavy petroleum fractions. 9

The art of pyrolytically cracking relatively heavy hydrocarbons to produce primarily gasoline or gas'is very extensive and it is recognized that most of the basic-principles of hydrocarbon catalysts are sensitive to sulfur poisoning and are quickly coated with carbonaceous materials which render them practically inert, This deposition of carbonaceous materials is frequently related to the type of decomposition reactions selectively fostered by the catalyst.

assignors to Universal Oil Products Com- A Chicago, 111., a corporation of Delaware Application October 31, 1938, Serial No. 238,075

The present invention is concerned with the manufacture of catalytic materials which are specially adapted to accelerate the cracking of heavy fractions of petroleum and other hydrocarbonaceous materials to increase the rate of production of high antiknock gasoline boiling range fractions and 'gaseous'by-products which contain unusually high percentages of readily polymerizable olefins which are a potential source of further gasoline yields. The preferred catalysts are characterized by selectivity in accelerating gasoline-forming; reactions rather than light gas-forming'reacti'ons, by their selectivity in producing high antiknock gasoline, by their refractory character which enables them to retain their catalytic properties under severe conditions of temperature and pressure, by their case and simplicity of manufacture and their exact reproducibility. l

In one specific embodiment the present invention comprises the manufacture of catalysts suitable for use in hydrocarbon conversion reactions, 9

more particularly the conversion of hydrocarbon knock-value and gases containing relatively high percentages of readily polymerizable olefins by preparing in the primary step a precipitated hydrated silica gel, treating and washing said silica gel with a reactant and water to effect substantially complete removal of alkali metal ions, adding a precipitated zirconia to the purified precipitated silica, then drying the composite catalytic material to remove a major portion of the water content, forming into particles of definite size and calcining the purified catalytic material.

We have found that zirconia-silica catalysts which maybe prepared byfthe several alternate methods described in more detail in the following paragraph, are rendered much more stable over long periods of use, and also more active and selective in'accelerati'ng gasoline forming reactions in cracking, when the originally precipitated hydrated silica which forms the primary material upon which the precipitated zirconia is subsequently disposed, is substantially freed from alkali metal ions which in the more general methods of preparation will be sodium ions inasmuch as the various sodium silicates comprise one of the more readily available raw materials for the manufacture of this type of catalyst. The purification treatment which constitutes one of the main features, of our invention is described in detail in later paragraphs. The subsequent deposition of zirconia upon the purified precipitated silica gel may be varied somewhat and the following is a summary of thealternate modes of operation which may be employed.

1. The purified precipitated hydrated silica gel may be suspended in a solution of a zirconium salt and zirconia deposited upon the suspended silica by the addition of volatile basic precipi- 1 tants, such as ammonium hydroxide, for example,

fractions containing substantially no gasoline into substantial yields of gasoline of high antior ammonium carbonate, ammonium hydrosulfide, ammonium sulfide, or other volatile basic precipitants generally may be employed.

2. The purified precipitated hydrated silica gel may be mixed while in the wet condition with a hydrated zirconia prepared, for example, by the addition'of volatile basic precipitants to a zirconium salt solution where the precipitated zirconia may be also treated and washed by the methods hereinafter described for the purification of the precipitated silica gel.

3. The purified precipitated silica gel may be added to a solution of a zirconium salt and zirconia precipitated by hydrolysis, with or without heating, or. the purified silica gel may be mixed with a sui'table amount of a zirconium salt, for example, and heated whereby zirconia will be -for other hydrocarbon reactions.

deposited asa-result'of the decomposition of the zirconium salt.

It can be seen from the above that various methods of admixing hydrated silica-and hydrated zirconia substantially free from alkali less with the exact conditions of precipitation solutions -insure the substantially complete absence of sodium or other-alkali metal ions.

and/or mixing,'purification treatment, and the ratio of zirconia to silica. For example, one

.preparation may furnish catalysts best suited for use in the cracking of heavy hydrocarbon fractions, another may be better adapted for use in reforming hydrocarbons substantially within the gasoline boiling point range, while still another preparation may be In the catalysts thus prepared the ratio of silica to zirco'nia by weight may range from 1 to l to to 1 or greater ratios may be used, active catalysts having been prepared in which the,

ratio 'is'as high as 50 to 1 so that in effect the zirconia may be considered to act as a promoter of the catalytic activity of the silica. It is to be recognized that very little is known positively concerning the mechanism of promoter action in catalysis and no attempt will be made herein to offer any definite reason for the observed" effect of the addition of varying amounts of zirconia to silica. There may be a joint promoter effect or it may be that the zirconia is the more active catalyst and is extensively dispersed in and on the silica in order to present a large surface.

An important feature of our invention resides in the factthat catalysts of greatly increased stability and efficiency in cracking reactions are produced when thereris substantially complete exclusion of alkali metal ions from the hydrated zirconia-silica masses prior to their drying and calcining to prepare them for service. In the present invention a precipitated hydrated silica gel substantially free from alkali metalions is used as the primary material or base for the subsequent deposition -of hydrated zirconia. Silica gel free from alkali metal ions may be prepared by the hydrolysis of silicon tetra-chloride, for example, but in the. more usual method thehydrated silica gel will be prepared by the acidification of alkali metal silicates, whereby better adapted alkali metal ions are unavoidably incorporated into the silica gel which are removed as one feature in the process of our invention. It is not positively known whether the'alkali metal compounds, such as those of sodium, are present in chemical combination or in an adsorbed state, but it has been definitely determined that their exclusion or removal is necessaryif catalysts of superior activity and stability are to be obtained.

It may be considered that the presence of these alkali metal ions may cause a sintering or. fusion of the surfaces of the primary composites of the catalytic, material at'elev'ated temperatures so that theporosity, of the catalyst particles is reduced or altered'with a-corresponding reduction in effective surface, considering the catalytic eflcts to be due'at least in part to surface action. However, such concepts areprincipally speculative in-viewof the difllculty of obtaining direct confirmatory evidence.

.Several alternative purification methods are I applicable to primary. hydratedsilica gels prepared by the acidification of. alkali metal silicate sorbed than alkali "metal ions.

to extract alkali metal impurities incorporated into the silica gel during its preparation by the formation of corresponding alkali metal salts. Thus a precipitated silica gel may be first washed with water to remove a 'major portion of the soluble impurities and subsequently treated with a mineral acid, for example, such as hydrochloric acid and water to remove the alkali metal ions. As an alternative purification method the primary precipitated hydrated silica may be treated with ammonium compounds or salts, such as ammonium chloride in solution or other halides, the sulfate, the nitrate, or the-acetate, so that alkali metal ions will not be substantially present in the primary gel when it has been suitably washed. Whether the alkali metal ions are present in the hydrated silica gel in a chemically combined or adsorbed condition, the alkali metal ions may be replaced by the ammonium ions which will be later expelled from combination or adsorption in subsequent treatment at elevated temperature.

Another alternate method forremoving alkali metal ions from the precipitated hydrated silica gel consists in treatingwith salts of multivalent metals which may replace the sodium or other alkali metals in the manner similar to that described in the case of ammonium compounds. For example, a primary gel having large amounts of alkali metal compounds present may be treated with a solution of salts of multivalent metals, more particularly zirconium, in which the metal forms the positive ion of the salt being used. In this mode of operation the multivalent metal used to replace the alkali metal ions is introduced into the catalytic material and is not removed at elevated temperatures as is the ammonium above described. whatsoever the purification method used, purified hydrated primary gels may be prepared by all the methods above described and substantially alkali metal-free zirconia has been added with'further processing according to the present invention to form catalysts suitable for hydrocarbon reactions.

The weight of evidence at hand on the mechanism leading to the replacement of alkali metals in the primary hydrated .Eel indicates that the alkali metals are held by'adsorption rather than by chemical bonds. This is indicated by the fact that the alkali metal ions are replaceable by ammoniumf or multivalent positive ions which are known in general to be more' strongly ad- This differentiates thisreplacement from the base exchange that occurs in the case or zeolites.-

After the zirconia has been mixed or deposited upon the purified hydrated silica gel and water washed, if desired, it may be recovered as a filter cake and dried at a temperature of the order of MO-300 F., more or less, after which it may be pressed and sized to recover particles of a convenient average size or formed into desired.

shapes by compression methods. It has been 'found that after the usual drying treatment the material ordinarily has a"tota1 water content of approximately 15 per cent which appears to correspond to the best workability of the material.

By'calcining the particles at temperatures of the order of 850-100,0 F. or higher, maximum activity of the catalyst is obtained and a further dehydration occurs so that, for example,

1y added. When about 4 gallons of the acid had been added gel began to form. The gel was then broken up' and agitated while adding half of the remaining acid, whereupon the viscosity vapors are able to penetrate to a considerable distance and. yet not so small that when the pores become clogged with carbonaceous deposits after a long period of service, they are diflicult to reactivate by oxidation. This structure is also retained after many alternate periods of use and reactivation as evidenced by the fact that the catalyst may be repeatedly reactivated by passing airor other-oxidizing gas over the spent particles to burn off deposits of carbonaceous material at temperatures as high as 1400 to 1600 F. without material loss of catalytic activity.

. was diminished to a pronounced degree and the remainin g acid added. After. standing for a while .the precipitated gel was directed to a filter press and filtered. The filter cake was broken up and treated to remove sodium ions.

as follows: Five gallons of water containing added hydrochloric acid was first used for washing, whereupon the gel was filtered and subsequently washed twice with 10 gallon portions of water. Subsequently the material was treated with 10 gallons of water containing added hydrochloric acid and ammonium chloride after which a wash with 10 gallons of water was used. Thir- According to the present process catalysts prepared by the general procedure described in the preceding paragraphs are utilized to advantage in cracking reactions when employed as filling material in tubes or chambers in the form of small pellets or granules. In the examples given below, wherein hydrocarbon fractions readily vaporizable at moderate temperatures without extensive decomposition are employed, thevaverabe particle size is within the range of 1 to'l0 mesh, which may apply either to small pellets of uniform size and short cylindrical shape or to particles of irregular size and shape produced by the grinding and sizing of the partially dehydrated materials. In some types of operation, the catalyst may be formed into smaller particles powdered.

The general procedure in cracking involves contacting the heated hydrocarbonaceous material with the catalyst and the subsequent fractionation steps involving separation of residuum and the further splitting up of the products into fixed gases, fractions of gasoline boiling range and heavier recycle stocks, may obviously be followed in the case of, the catalysts comprised within the scope of the invention. In using these catalysts moderate temperatures, relativelylow pressures and high throughputs are to be expected in comparison with the strictly thermal cracking processes in use at the present time.

V The following examples of preparation of-the types of catalysts tion are given to indicate their novelty and utility although notfor the purpose of limiting the invention in exact agreement with the data introduced.

- Example I w A catalyst prepared according to the present teen hundred and fifty-six grams of this filtered gel corresponding to 3 moles of silica was slurried in 8 liters of water and 170 cc. of a solution of ZIOClz (corresponding to 0.12 mole ZrOz) in excess hydrochloric acid added. After-prolonged" agitation of this suspension a solution of 52' cc. concentrated ammonium hydroxide in 1200 cc. of water was slowly added while agitating. The final liquid was alkaline to litmus. The precipitated mass was then filtered and further washed and a portion "0f the filter cake was dried at 4 approximately 300 F.,.p'repared into 6-10 mesh peculiar to the present inveninvention comprising 4 moles of zirconiadeposited on 100 moles of hydrated silica was prepared according to the following general procedure:

A silica hydrogel p'recip'tated from a sodium siilcate solution was washed and treated with dilute acid and ammonium chloride solution to substantially remove alkali metal ions, and the purified hydrated silica wasv suspended ina so.-

lution of a zirconium salt andzirconia pre'cipi- 'tated. 7

Eighteen liters of a commercial grade of sodium silicate was diluted with gallons of distilled water and agitated, while dilute hydrochloric acid containing 6 liters of concentrated hydrochloric acid in5 gallons of water was slowgranules for a test, and .subsequently calcined at approximately 932 The following results were obtained when processing a 37 A P. I. gravity gas-oil in a oncethrough operation:

Cracking data and results Run 1 Run 2 Temperature F 932 932 Gasoline, 400 F. E. P.:

Volume percent 25. 3 23. 0 A. P. I. gravity, 60 F 58.8 59. 5 Octanenumber (motor method) 78. 6 78. 6 Gases (boiling range below +l0 0.):

Molecular weight 36. 5 33. 7 Propane and butenes- We1ght percent of charge 3. 9 3. 6 Gas-oil recovered (recycle stock): v Volume percent 73. 8 75. 5 A. P. l. gravity, 60 F"... 37. 5 37. 5

Example II In the following example a silica-zirconia catalyst was prepared containing 16 moles of Zl'Oz deposited upon moles of SiOz. The general method involved the purification of a silica gel with subsequent precipitation ofzir- I conia in the presence of the-suspended purified hydrogel. I

A silica gel was prepared and purified as follows: Eight hundred and thirty grams of a commercial waterglass was diluted using 6 liters of water. A liter of 2.5 molar hydrochloric acid was then slowly added to the sodium silicate solution while agitating. After the addition of all the acid the liquid was acidic to blue litmus. The mixture was filtered and the filter cake was washed several times using 5 liters of water for each washing. The precipitated gel was then washed with 5 liters of water containing A equivalent of hydrochloric acid, which operation was performed twice. Subsequently the j precipitated material was washed several times with 5 liter portions of water. Five hundred and thirty-seven grains of the hydrated silica, corresponding to 1.35 moles of SiOz, was suspended in 750 cc. of water and a solution of 67.3 grams of zirconyl nitrate in 1000 cc. of water added. After prolonged agitation 757 cc. of 1.006 normalammonium hydroxide was added while agitating so that the final liquid was basic to litmus.

The precipitated materialwas dried at approxi-' bed at a liquid space velocity per hour. of ap In a once-through operation proximately, 4. there was produced 28.7% of 400 F. end-point gasoline having an octane: number of 78.1.

- There was also produced 5.2% by weight of "the original charge of readily polymerizable 3 and 4 carbon atom olefins.

Example III The method used in this example is to prepare and purify a silica gel as in Example II- above and then suspend in a solution of a zirconium salt, draining the precipitate and drying at approximately 300 F.

A purified precipitated hydrogel is prepared. exactly as indicated in the above example and suspended in 500 cc. of a solution containing 50 grams of ZIOClz. After thorough agitation the excess liquid is drained off by filtration and the filter cake dried at approximately 300 F. The dried material is then pressed in a hydraulic pressand particles of 6-10 mesh produced from the pressed material. The particles are then calcined at approximately 932 F. and subsequently disposed in a catalyst chamber for a test.

Using the same gas-oil as was used in EX- ample II, a yield of 25% by volume of 400 F. end-point gasoline may be obtained in a single pass, the octane number being the same as above with a 4% yield of readily polymerizable 3 and 4 carbon atom olefins.

We claim as our invention:

1. A process for the manufacture of catalysts suitable for use in hydrocarbon conversion reactions, which comprises precipitating a silica hydrogel from a solution of an alkali metal silicate by the acidification thereof, freeing said hydrogel substantially completely of alkali metals, suspending the purified hydrogel in a solution of a zirconium salt and precipitating zirconia by means of a volatile basic precipitant, heating the precipitated material to remove a major portion of the water content, forming particles of definite size, and calcining above a temperature of about 800F.

i 2. A process for the manufacture of catalysts suitable for use in hydrocarbon conversion ,reactions, which comprises precipitating a silica hydrogel from a solution of an alkali metal silicate by the acidification thereof, washing and treating said hydrogel with asufficient quantity of an acidic solution and water to substantially completely remove all alkali metals therefrom, suspending the purified hydrogel in a solution of a zirconium-'saltand tpr'ecipitatin'g zirconia by means of a volatile basic precipitant, heating'the precipitated material to remove a major portion of the water content, forming particles of definite size, and calcining above a temperature of about 800 F. I 3. A process for the manufacture of catalysts suitable for use in hydrocarbon conversion reactions, which comprises precipitating a silica hydrogel from a solution of an alkali metal'silicate by the acidification thereof, washing and treating said hydrogel with a sufficient quantity of a solution offan ammonium compound and water to substantially completely remove all al-' kali metals therefrom, suspending the purified hydrogel in a solution of a zirconium salt and precipitating zirconia bymeans of a volatile'basic precipitant, heating the precipitated material to remove a major portion of the water content, forming particles of definite size, and calcining above a temperature of about 800 F.

4. A process for the manufacture of catalysts suitable for use in hydrocarbon conversion reactions, which comprises precipitating a silica' hydrogel from a solution of an alkali metal silicate by the acidification thereof, washing and treating said hydrogel with a sufiicient quantity of a solution of a salt of a multivalent metal and water to substantially completely remove all alkali metals therefrom, suspending the purified hydrogel in a solution of a zirconium salt and precipitating zirconia by means of a volatile basic precipitant, heating the precipitated material to remove a major portion of the water content, forming particles of definite size, and calcining above a temperature of about 800 F. 5. A process for the manufacture of catalysts which comprises precipitating a silica hydrogel from a solution of an alkali metal silicate, freeing the hydrogel substantially completely of alkali metal ions, suspending the thuspurified silica hydrogel in a zirconium salt solution, adding a Volatile basic precipitant to the suspension to deposit hydrated zirconia on the silica hydrogel, and calcining the resultant silica-zirconia mixture.

6. A process for the manufacture of catalysts which comprises precipitating a silica hydrogel from a solution of an alkali metal silicate, freeing -the hydrogel substantially completely of alkali metal ions, suspending the thus purified silica hydrogel in a zirconium salt solution, adding a volatile basic precipitant to the suspension to deposit hydrated zirconia on the silica hydrogel, heating the resultant wet precipitate mixture sufficiently to remove the major portion of its water content, formin the partially dehydrated mixture into masses of predetermined size, and calcining said masses.

7. A process for the manufacture of catalysts which comprises suspending precipitated silica hydrogel in a zirconium salt solution, adding a volatile basic precipitant to the suspension to deposit hydrated zirconia on the silica hydrogel, and calcining the resultant silica-zirconia mixture.

EDWARD C. LEE. JACOB ELSTON AHLBLRG. 

